Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
ELECTROMAGNETICALLY SHIELDED BUILDING
BACKGROUND OF T~E INVENTION
This invention relates to a building having an
electromagnetic shield structure well-suited for
application to an information network system utilizing
electromagnetic waves, and more particularly to an
electromagnetically shielded building for enhancing the
electromagnetic shielding performance of an external
wall.
In many modern buildings, information generally is
communicated between the interior and the outside of
the building by making joint use of information
communicating equipment such as multiple electronic
exchanges and computers. With the increasing value of
information, diversification of user needs and
increasingly individual nature thereof, the amount of
information involved in such communication is growing.
Under these circumstances, how to transmit the
necessary information rapidly and at low cost where
large-scale buiLdings are involved has become of prime
importance. In an effort to satisfy this need, data
highway-type information networks utilizing optical
fiber cables or coaxial cables have been studied and
proposed-
However, with a data highway system utilizing
optical fiber cables or coaxial cables, the cables must
be stretched throughout all parts of the building to
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reach the various pieces of communication equipment.
Extra time is needed to complete the work and
additional expenses are required to lay these cables.
If electromagnetic waves are used to transmit
information within the building, laying cables is
unnecessary but the radio waves are limited to a certain
range owing to the emission of electrical noise waves from
such a building. Another problem is that the
communication system may malfunction due to electric waves
from outside the building, television intermediate
frequencies from inside the building, electric waves from
wireless microphones, and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an
electromagnetic shielded building in which information
can be communicated using electric waves of any
frequency over a wide range of frequencies.
Another object of the present invention is to
provide a method of electromagnetically shielding a
building.
Still another object oE the present invention is
to provide an electromagnetic shielding structure of an
external wall employing a curtain wall, in which an
external wall using a curtain wall the structure
whereof is similar to that of the conventional curtain
wall is constructed in the form of a perfect
electromagnetic shielding layer.
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In accordance with a preferred embodiment of the
invention, there is provided an electromagnetically shielded
building comprising a building portion constituted by an
S electromagnetic shielding structure, all or a part of the
interior of the building being formed as an
electromagnetically shielded space, communications equipment
for communications within the building, and an electromagnetic
signal transmission medium in the shielded space arranged so
that sets of the communications equipment communicate with
each other within the building using electromagnetic waves
transmitted through the transmission medium.
According to other embodiments of the invention, the
outer peripheral of the electromagnetically shielded building
is constituted by an electromagnetic shielding structure
comprising ferrite-containing concrete, or mesh-containing
concrete.
According to another preferred embodiment of the
building, the outer peripheral walls of the building are an
electromagnetic shielding structure, and electromagnetic
curtain walls are fixed to the outer building walls by anchor
bolts and metal fastener, affixing an electrically conductive
annular ring to a side face of the curtain wall, and
electrically integrating mutually adjacent curtain walls.
According to another preferred embodiment of the
building, the signal transmission medium comprises a coaxial
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cable laid so as to pass through each floor of the building,
and leakage coaxial cables or antennas stretched along the
ceiling of each floor and connected to the coaxial cable via
branching devices.
In accordance with the invention, the body of a
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buildin~ is construct~d of concrete containing an
electromagnetic shielding member. In another method, the
external wall of a buildin~ is constructed of PC, precast
concrete, panels having an imbedded mesh, the mesh in the
PC panels is electrically connected to fixing members of
the building body, and the PC panels of upper and lower
floors are electrically connected and grounded.
Alternatively, use is made of curtain walls constructed
of electromagnetic shielding members and fixed to the
body of a building by anchor bolts via metal fasteners.
Electrically conductive cushions are affixed to the
side faces of the curtain walls, and`neighboring
curtain walls are electrically integrated to form an
electromagnetic shielding space. The communication
system includes a coaxial cable laid so as to pass
through the floors of the building, leakage coaxial
cables stretched along the ceiling of each floor and
connected via to the coaxial cable branching devices,
and antennas. These cables and antennas are employed
as a transmitting medium to permit communication within
the building by utilizing electric waves.
In accordance with the above-described
arrangements, the invention blocks electric waves at
the body of the building by the formation of an
electromagnetic shield. As a result, electric waves
will not leak from the building even if information is
communicated within the building using any desired
frequency over a wide frequency band. In addition,
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communication equipment within the building will not
malfunction due to electric waves penetrating the
building from outside. When the mesh is imbedded in
the PC panels, the meshes are electrically connected to
the fixing members of -the building body and the PC
panels of upper and lower floors are electrically
interconnected and grounded, an electromagnetic
shielding effect can be obtained at the external wall
of the building through simple construction work~
If the curtain wall is adopted as the external
wall, a curtain wall having an electromagnetic
shielding function is used and the electrica]ly
conductive cushion is affixed to the side face of the
curtain wall. Then, by securing the curtain wall to
the body of the building by the anchor bolts via the
metal fasteners, mutually adjacent curtain walls can be
electrically integrated. By adopting this arrangement,
the external wall can be assembled through the
conventional method, i.e. by securing the curtain walls
to the metal fasteners by the anchor bolts and then
assembling the external wall, at the same time that the
entirety of the external wall is furnished with the
electromagnetic shielding property.
In the communication system, the leakage coaxial
cables stretched along the ceiling of each floor serve
as antennas and the antennas are interconnected by a
coaxial cable via branching devices. As a result,
electric wave signals emitted by the communication
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equipment on each floor are transmitted by the antennas
of the leakage coaxial cables and received by the
communication equipment on other floors through the
antennas of the leakage coaxial cables on these other
floors.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a view for describing an embodiment of a
building the body of which is electromagnetically
shielded in accordance with the present invention;
Fig. 2 is a view illustrating an embodiment of the
electromagnetic shielding of a building body in
accordance with the present invention;
Fig. 3 is a view illustrating another embodiment
of the electromagnetic shielding of a building body in
accordance with the present invention;
Figs, 4A, 4B and 4C are views useful in describing
the electromagnetic shielding of building openings in
accordance with the present invention;
Figs. 5A and 5B are views for describing an
embodiment of another electromagnetic shielding method
according to the present invention; and
Fig. 6 is a view illustrating an embodiment of the
electromagnetic shielding structure of an external wall
using a curtain wall in accordance with the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the invention will now be described
with reference to the drawings.
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As shown in Fig. 1, a building in accordance with the
invention includes a body 1, pipe shafts 2-1 through 2-n
for electrical equipment (each electrical equipment pipe
shaft being referred to as an EPS hereinafter), a coaxial
cable 3, branching devices 4, leakage coaxial cables S,
and a grounding plate 6. Figs. 2, 3 and 4, numeral 7
denotes a mesh-containing concrete, 8 a mesh, 9
ferrite-containing concrete, 10 ferrite, 11 a doorway,
12 a revolving door, and 13 a window.
In the building shown in Fig. 1, the body 1 is
electromagnetically shielded, as indicated by the
dashed line in Fig. 1, in such a manner that electric
waves from communications equipment within the building
will not lea~ from the building~ The leakage coaxial
cables 5 are stretched along each ceiling and are
connected to the coaxial cable 3 via the branching devices
4. By using electric waves transmitted through these
cables, communication is possible among communications
equipment installed on each floor without requiring
that cables be laid to interconnect the equipment. In
particular, if the entirety of the building body 1 is
furnished with an electromagnetic shielding capability,
the transmission and reception of electric waves
between upper and lower floors will be blocked by the
body 1. For this reason, the leakage coaxial cables 5
are provided to perform a relay function on each floor.
A community television cable ordinarily used in
buildings can be employed as the coaxial cable 3, which
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is passed through the EPSs 2-1 through 2-n. Though not
shown, a community antenna is connected to the head end
of the coaxial cable 3, and television receivers or the
like are connected to the coaxial cable 3 via the
branching devices 4. Accordingly, a signal received
from the community antenna is distributed by the
branching devices 4 via the head end and coaxial cable
3.
In accordance with the invention, the emission of
electrical noise to the exterior of the buildin~ is
eliminated by electromagnetically shielding the body 1.
Therefore, merely stretching the leakage coaxial cables
5 along the ceiling of each floor as antennas and
connecting them to the branching devices 4 makes it
possible to freely use even electric waves in a
frequency band subjected to restrictions in accordance
with law, thus enabling these electric waves to be used
for the communication of information within the
building. The invention thus makes it possible to
employ electric waves of any economical, convenient
easy-to-use freguency band.
A specific method of electromagnetically shielding
the body of a building is shown in Fig. 2, in which
the body 1 is constructed of concrete 7 having an
imbedded mesh 8. An alternative is shown in Fig. 3, in
which the body 1 is constructed of concrete 9 in which
ferrite 10 has been mixed. In a case where the body is
constructed of the mesh-containing concrete 7, a method
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using PC panels for the external wall, a method using
PC panels for the e~ternal wall for, or a method using
a mesh form can be employed. Generally, in an ordinary
building body, electric waves are attenuated by 5 - 20
ds. However, if the aforementioned ferrite-containing
concrete or mesh-containing concrete is used to
construct the body, as set forth above, noise removal
in a building having such a body can be raised to 60
dB. This makes it possible to avoid emission of
electrical noise from the building and to prevent the
communication system within the building from being
adversely affected by electric waves from outside the
building.
Even if the body of a building has an
electromagnetic shielding structure, the building has
openings in its body, such as a doorway 11 and window
13, as shown in Fig. 4A, and electric waves pass
through these openings. Accordingly, it is necessary
that these openings also be electromagnetically
shielded. To this end, a revolving door method can be
employed, as shown in Fig. 4B, or a double-door can be
employedr as shown in Fig. 4C. In the latter method,
the linear propagation property of high-frequency
electric waves is utilized to attenuate the energy o~
the electric waves during their transit from the first
door to the second door, or an interlocked arrangement
is adopted in which one o the two doors is always kept
closed. At a window opening, it will suffice if the
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glass contains electrically conductive mesh or makes
use of an electrically conductive tape that also
conserves energy. Adopting the above-described
expedients prevents electric waves from passing in and
out of the building through the doorways and windows to
provide the overall building with an electro-
magnetically shielded structure.
Another example of an opening in the body of a
building is a duct. A duct can be electromagnetically
shielded by using a metal mesh in the duct filter. As
for portions where gaps are formed, electromagnetic
shielding can be provided by using an electrically
conductive rubber packing or electrically conductive
brushes. These portions can be electromagnetically
shielded by any appropriate method.
Figs. 5A, 5B are views for describing an
embodiment of another method of electromagnetically
shielding a building, in which 21 represents a PC
(precast concrete) panel, 22 a conductor, 23 a
fastener, 24 a slab and 25 a mesh.
In Figs. 5A, 5B,, the mesh 25 having the conductor
22 led out therefrom it imbedded in the PC panel 21,
which is attached to the slab 24 by a fastener 23.
When the PC panel 21 is attached to the slab 24, the
~ onductor 22 is connected to the fastener 23, and the
meshes 25 in PC panels 21 of the upper and lower floors
are electrically interconnected via the fasteners 23.
By grounding the mesh 25 in the PC panel 21 on the
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lowermost floor, all of the meshes 25 in the PC panels
21 covering the building are grounded to improve the
~lectromagnetic shielding performance of the building.
In addition to the above embodiments, it is of
course possible to provide an external wall with an
electromagnetic shielding structure in accordance with
the invention. For example, if a curtain wall is used
as the external wall, the prior-art structure is such
that cushion (an annular ring) is attached to the side
face of a conventional curtain wall, a curtain wall
edge portion is placed on the cushion, and this is
fastened by securing anchor bolts to fasteners fixed to
the building body side. Therefore, mutually adjacent
curtain walls will not be electrically integrated
merely by constructing an external wall of curtain
walls using electromagnetic shielding members, and
electric waves will leak from the gaps between the
curtain walls. Thus, the overall external wall will
have a very poor electromagnetic shielding effect. An
example of an electromagnetic shielding structure
capable of solving this problem will now be described.
Fig. 6 is a view showing an embodiment of an
electromagnetic shielding structure of an external wall
using a curtain wall for a building in accordance with
the invention. Numerals 31, 39 denote PC curtain
walls, 32, 34 anchor bolts, 33 a faster, 34 an annular
ring, 35 a back-up member, 36 a caulking material, 37
the beam of a steel frame, and 38 a crossover
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connecting wire.
Fig. 6 shows a transverse section of the
connection between an upper-side PC curtain wall 31 and
a lower-side curtain wall 39. In the external wall
structure using the PC curtains walls shown in Fig. 6,
the fastener 33 is secured to the steel frame beam 37,
and the PC curtain walls 31, 39 are fixed to the
fastener 33 by anchor bolts 3~, 40. sy securing the PC
curtain walls 31, 39 to the fastener 33 with the
annular ring 34 affixed to the side face of the PC
çurtain walls 31, 39, the gap between the panels is
closed by the annular ring wound on -the side face, as
illustrated. A gap near the surface of the external
wall is filled with the back-up member 35 and with the
caulking material 36 disposed on the back-up member.
In the electromagnetic shielding structure of an
external wall using a curtain wall in accordance with
the invention, electromagnetic shielding members are
used in the PC curtain walls 31, 39, the main body i
O made an electromagnetic shielding layer, and an
electrically conductive cushion is used as the annular
ring 34. In a case where the PC curtain wall has the
annular ring 34 affixed to the side face with an
electrical insulator layer interposed therebetween, the
annular ring 34 and anchor bolt 32 are connected using
the crossover wire 38, thereby electrically integrating
the electromagnetic shielding layers on the main bodies
of the PC curtain walls 31, 39 at the anchor bolts 32,
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40 and fastener 33. The annular ring 34 is
electrically integrated with the anchor bolt 32 by the
crossover wire 38. An electrically integrated
structure is obtained by using an electromagnetic
shielding member as the back-up member 35.
Since the annular ring is wound on the side face
of the PC curtain walls, a gap at the joint of the left
and right PC curtain walls is closed by an annular
ring, back-up member and caulking material, just as
shown in Fig. 6, in order to obtain an electrically
integrated structure.
By thus providing the periphery of a building with
an electromagnetic shielding structure as set forth
above, the communication of information utilizing
electric waves can be carried out freely within the
building.
In the system using the branch devices shown in
~ig. 1, the branch devices connected to the community
coaxial cable possess reverse-connection loss in order
to reduce interference among one another. More
specifically, owing to reverse-connection loss, signals
flow between the head end and each set of equipment,
but signals do not readily flow between one set of
equipment and another. Ordinarily, reverse-connection
loss is set in accordance with the FM or television
frequency band of 80 M~z or greater for community use
and is effective for high frequencies of 10 MHz or
more.
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In a case where a frequency band of the coaxial
cable other than the FM or television frequency band is
adopted for the communication line, there will be a
frequency band in which reverse-connection loss is
effective, i.e. a high-frequency band of 10 MHz or
more, and a frequency band in which reverse-connection
loss is not effective, i.g. a low-frequency band of
several MHz or less.
Accordingly, if the high-frequency band is used,
it is necessary that the head end be provided with a
repeater and that the transmission of information
between communication controllers be carried out
through the repeater. In other words, assume that a
signal transmitted by a communication controller is an
up-signal and that a signal received thereby is a
down-signal. By using the repeater to switch the
up-signal for the down-signal instead of up- and
down-carrier frequencies, a single transmission line
will enable communication between communication
controllers.
If the low-frequency band is used, on the other
hand, the repeater is unnecessary. However, a base
band FSK (frequency shift keying) system is employed
for signal transmission between communication
controllers so that FM and television broadcasts will
not be adversely affected. More specifically, when
information is transmitted via a television community
axial cable by "1", "O" pulses, the pulse signal
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contains high-Erequency ~mpone~ts, as a result of
~hich FM and television broadcasts are adversely
affected. With the base band FSK system, however, a
frequency shift (FS) takes place in a frequency band of
several MHz or less in accordance with the "1", "0"
information, so that there are no high-frequency
components detrimental to FM and television broadcasts.
The present invention is not limited to the above-
described embodiments but can be modified in various
ways. For example, instead of leading out a conductor
from a mesh imbedded in a PC panel, the mesh and an
imbedded bolt used for connection to the fastener can
be electrically connected beforehand at the factory.
Furthe~, in the above-described embodiments, the
annular ring and anchor bolt are connected solely on
the lower side of the curtain wall. However, a similar
connection can be made on the upper side as well. In
addition, if the annular ring is affixed to the side
face of the PC panel without an intervening insulating
layer, the crosswire between the annular ring and
anchor bolt can be deleted.
In accordance with the invention, the body of a
building is electromagnetically shielded and
communication using electric waves of any frequency is
carried out inside the building. This enables
communication using a wide frequency band and permits
communication lines to be increased without limitation.
Since the laying of communication cables is
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unnecessary, building construction is facilitated and
construction costs can be reduced. Since an
electromagnetic shielding effect is obtained thanks to
the mesh imbedded in the PC panels, work on-site is
simplified, the term of construction is shortened and
expenses are reduced.
The entire external wall surface using curtain
walls can be constructed as an electromagnetic
shielding layer since an electrically conductive
cushion is used as the annular ring wound on the side
face of the curtain wall. If an insulating layer is
interposed between the electrically conductive cushion
and the electromagnetic shielding layer of the curtain
wall, the electromagnetic shielding effect of the
external wall can still be assured by connecting the
electrically conductive cushion and the anchor bolt
with the crossover connection wire. Moreover, by
connecting the electrically conductive cushion and
anchor bolt in advance before construction of the
external wall, the latter can be constructed, and the
electromagnetic shielding effect can be obtained
simultaneously, merely by securing the PC curtain wall
to the fastener by means of the anchor bolts, just as
in the prior art.
2S In the communication system, a coaxial cable
ordinarily laid in a building is utilized. Leakage
coaxial cables and antennas need only be provided on
the ceiling of each floor and connected to the
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aforementioned coaxial cable via branch devices. This
reduces the expenses required for the communication
mediilm and eliminates some oE the labor involved in
construction work. If wireless transceivers are used,
communication within the building becomes possible.
This makes it unnecessary to modify the partitions and
equipment arrangements on each floor as well as the
wiring of communication lines when tenants change. The
overall result is a very flexible system.
